| Message ID | 20101208160110.1b0c7c64@doriath |
|---|---|
| State | New |
| Headers | show |
On 12/08/2010 12:01 PM, Luiz Capitulino wrote: > Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. > This patch adds a simple check and error message (much like the 2047 limit on > 32-bit hosts) on ram_size in the control path after we determine we're > not using kvm > > Upstream qemu-kvm is affected if using the -no-kvm option; this patch address > the segfault there as well. > > Signed-off-by: Ryan Harper<ryanh@us.ibm.com> > Signed-off-by: Aurelien Jarno<aurelien@aurel32.net> > --- > NOTE: this patch was applied in the v0.12.x branch, but it seems it got > lost for master > No, it was intentional. We should fix the segv, this is not a known limitation but rather a bug. Regards, Anthony Liguori > vl.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/vl.c b/vl.c > index 2dbb6db..bb9c21c 100644 > --- a/vl.c > +++ b/vl.c > @@ -5792,6 +5792,12 @@ int main(int argc, char **argv, char **envp) > fprintf(stderr, "failed to initialize KVM\n"); > exit(1); > } > + } else { > + /* without kvm enabled, we can only support 4095 MB RAM */ > + if (ram_size> (4095UL<< 20)) { > + fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM can be simulated\n"); > + exit(1); > + } > } > > if (qemu_init_main_loop()) { >
On Wed, 08 Dec 2010 12:23:12 -0600 Anthony Liguori <aliguori@linux.vnet.ibm.com> wrote: > On 12/08/2010 12:01 PM, Luiz Capitulino wrote: > > Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. > > This patch adds a simple check and error message (much like the 2047 limit on > > 32-bit hosts) on ram_size in the control path after we determine we're > > not using kvm > > > > Upstream qemu-kvm is affected if using the -no-kvm option; this patch address > > the segfault there as well. > > > > Signed-off-by: Ryan Harper<ryanh@us.ibm.com> > > Signed-off-by: Aurelien Jarno<aurelien@aurel32.net> > > --- > > NOTE: this patch was applied in the v0.12.x branch, but it seems it got > > lost for master > > > > No, it was intentional. We should fix the segv, this is not a known > limitation but rather a bug. A TCG bug, I presume? > > Regards, > > Anthony Liguori > > > vl.c | 6 ++++++ > > 1 files changed, 6 insertions(+), 0 deletions(-) > > > > diff --git a/vl.c b/vl.c > > index 2dbb6db..bb9c21c 100644 > > --- a/vl.c > > +++ b/vl.c > > @@ -5792,6 +5792,12 @@ int main(int argc, char **argv, char **envp) > > fprintf(stderr, "failed to initialize KVM\n"); > > exit(1); > > } > > + } else { > > + /* without kvm enabled, we can only support 4095 MB RAM */ > > + if (ram_size> (4095UL<< 20)) { > > + fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM can be simulated\n"); > > + exit(1); > > + } > > } > > > > if (qemu_init_main_loop()) { > > >
On 12/08/2010 12:27 PM, Luiz Capitulino wrote: > On Wed, 08 Dec 2010 12:23:12 -0600 > Anthony Liguori<aliguori@linux.vnet.ibm.com> wrote: > > >> On 12/08/2010 12:01 PM, Luiz Capitulino wrote: >> >>> Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. >>> This patch adds a simple check and error message (much like the 2047 limit on >>> 32-bit hosts) on ram_size in the control path after we determine we're >>> not using kvm >>> >>> Upstream qemu-kvm is affected if using the -no-kvm option; this patch address >>> the segfault there as well. >>> >>> Signed-off-by: Ryan Harper<ryanh@us.ibm.com> >>> Signed-off-by: Aurelien Jarno<aurelien@aurel32.net> >>> --- >>> NOTE: this patch was applied in the v0.12.x branch, but it seems it got >>> lost for master >>> >>> >> No, it was intentional. We should fix the segv, this is not a known >> limitation but rather a bug. >> > A TCG bug, I presume? > Dunno, that's why we shouldn't just paper over it. Regards, Anthony Liguori > >> Regards, >> >> Anthony Liguori >> >> >>> vl.c | 6 ++++++ >>> 1 files changed, 6 insertions(+), 0 deletions(-) >>> >>> diff --git a/vl.c b/vl.c >>> index 2dbb6db..bb9c21c 100644 >>> --- a/vl.c >>> +++ b/vl.c >>> @@ -5792,6 +5792,12 @@ int main(int argc, char **argv, char **envp) >>> fprintf(stderr, "failed to initialize KVM\n"); >>> exit(1); >>> } >>> + } else { >>> + /* without kvm enabled, we can only support 4095 MB RAM */ >>> + if (ram_size> (4095UL<< 20)) { >>> + fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM can be simulated\n"); >>> + exit(1); >>> + } >>> } >>> >>> if (qemu_init_main_loop()) { >>> >>> >> >
On Wed, Dec 08, 2010 at 04:27:45PM -0200, Luiz Capitulino wrote: > On Wed, 08 Dec 2010 12:23:12 -0600 > Anthony Liguori <aliguori@linux.vnet.ibm.com> wrote: > > > On 12/08/2010 12:01 PM, Luiz Capitulino wrote: > > > Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. > > > This patch adds a simple check and error message (much like the 2047 limit on > > > 32-bit hosts) on ram_size in the control path after we determine we're > > > not using kvm > > > > > > Upstream qemu-kvm is affected if using the -no-kvm option; this patch address > > > the segfault there as well. > > > > > > Signed-off-by: Ryan Harper<ryanh@us.ibm.com> > > > Signed-off-by: Aurelien Jarno<aurelien@aurel32.net> > > > --- > > > NOTE: this patch was applied in the v0.12.x branch, but it seems it got > > > lost for master > > > > > > > No, it was intentional. We should fix the segv, this is not a known > > limitation but rather a bug. > > A TCG bug, I presume? > Do you have more details about this issue and how to reproduce it? Support for more than 4GB of memory has been added a few years ago, and I am not able to reproduce the problem anymore (I have booted a 64-bit guest with 6GB of RAM, and make sure the guest use the whole memory). I guess TCG itself is fine, but there might be a bug in the MMU emulation in some cases. I also noticed that now i386-softmmu has been artificially limited to 2047MB. Tthis configuration used to support up to 64GB of RAM (PAE) on 64-bit hosts.
* Aurelien Jarno <aurelien@aurel32.net> [2010-12-25 16:37]: > On Wed, Dec 08, 2010 at 04:27:45PM -0200, Luiz Capitulino wrote: > > On Wed, 08 Dec 2010 12:23:12 -0600 > > Anthony Liguori <aliguori@linux.vnet.ibm.com> wrote: > > > > > On 12/08/2010 12:01 PM, Luiz Capitulino wrote: > > > > Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. > > > > This patch adds a simple check and error message (much like the 2047 limit on > > > > 32-bit hosts) on ram_size in the control path after we determine we're > > > > not using kvm > > > > > > > > Upstream qemu-kvm is affected if using the -no-kvm option; this patch address > > > > the segfault there as well. > > > > > > > > Signed-off-by: Ryan Harper<ryanh@us.ibm.com> > > > > Signed-off-by: Aurelien Jarno<aurelien@aurel32.net> > > > > --- > > > > NOTE: this patch was applied in the v0.12.x branch, but it seems it got > > > > lost for master > > > > > > > > > > No, it was intentional. We should fix the segv, this is not a known > > > limitation but rather a bug. > > > > A TCG bug, I presume? > > > > Do you have more details about this issue and how to reproduce it? At the time of the bug, it was something simple like: qemu-system-x86_64 -m 4097 -hda /dev/null we'd get an imediate segfault. As you say, I'm not seeing it now on current git; I'll see about bisecting to see if we did get a fix for the issue. > > Support for more than 4GB of memory has been added a few years ago, > and I am not able to reproduce the problem anymore (I have booted a > 64-bit guest with 6GB of RAM, and make sure the guest use the whole > memory). I guess TCG itself is fine, but there might be a bug in > the MMU emulation in some cases. > > I also noticed that now i386-softmmu has been artificially limited to > 2047MB. Tthis configuration used to support up to 64GB of RAM (PAE) > on 64-bit hosts. > > -- > Aurelien Jarno GPG: 1024D/F1BCDB73 > aurelien@aurel32.net http://www.aurel33.net
* Ryan Harper <ryanh@us.ibm.com> [2011-01-04 09:49]: > * Aurelien Jarno <aurelien@aurel32.net> [2010-12-25 16:37]: > > On Wed, Dec 08, 2010 at 04:27:45PM -0200, Luiz Capitulino wrote: > > > On Wed, 08 Dec 2010 12:23:12 -0600 > > > Anthony Liguori <aliguori@linux.vnet.ibm.com> wrote: > > > > > > > On 12/08/2010 12:01 PM, Luiz Capitulino wrote: > > > > > Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. > > > > > This patch adds a simple check and error message (much like the 2047 limit on > > > > > 32-bit hosts) on ram_size in the control path after we determine we're > > > > > not using kvm > > > > > > > > > > Upstream qemu-kvm is affected if using the -no-kvm option; this patch address > > > > > the segfault there as well. > > > > > > > > > > Signed-off-by: Ryan Harper<ryanh@us.ibm.com> > > > > > Signed-off-by: Aurelien Jarno<aurelien@aurel32.net> > > > > > --- > > > > > NOTE: this patch was applied in the v0.12.x branch, but it seems it got > > > > > lost for master > > > > > > > > > > > > > No, it was intentional. We should fix the segv, this is not a known > > > > limitation but rather a bug. > > > > > > A TCG bug, I presume? > > > > > > > Do you have more details about this issue and how to reproduce it? > > At the time of the bug, it was something simple like: > > qemu-system-x86_64 -m 4097 -hda /dev/null > > we'd get an imediate segfault. As you say, I'm not seeing it now on > current git; I'll see about bisecting to see if we did get a fix for the > issue. I attempted to bisect, but there a couple commits around where the issue was fixed that broke git bisect =( That narrowed it down to about 5 commits to check. This the last git commit where I can reproduce the segfault with the above test case (qemu invocation). commit 0aef4261ac0ec9089ade0e3a92f986cb4ba7317e Author: Aurelien Jarno <aurelien@aurel32.net> Date: Thu Mar 11 21:29:42 2010 +0100 target-ppc: fix evsrwu and evsrws (second try) Signed-off-by: Aurelien Jarno <aurelien@aurel32.net> The next 4 commits don't compile so they are untest-able: commit 14f24e1465edc44b9b4d89fbbea66e06088154e1 - fails to build with: - ./configure --target-list=x86_64-softmmu && make clean && make /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS make[1]: *** [exec.o] Error 1 make: *** [subdir-x86_64-softmmu] Error 2 commit 7bc7b099dfa38a856b1bc892c0f9f3d6fe28e170 - fails to build with: - ./configure --target-list=x86_64-softmmu && make clean && make /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS make[1]: *** [exec.o] Error 1 make: *** [subdir-x86_64-softmmu] Error 2 commit b9f83121a13153536d886305414b540460c34508 - fails to build with: - ./configure --target-list=x86_64-softmmu && make clean && make /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS make[1]: *** [exec.o] Error 1 make: *** [subdir-x86_64-softmmu] Error 2 commit 5270589032f450ae7c3448730855aa18ff68ccff - fails to build with: - ./configure --target-list=x86_64-softmmu && make clean && make /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS make[1]: *** [exec.o] Error 1 make: *** [subdir-x86_64-softmmu] Error 2 And this commit compiles and the test case no longer segfaults. So I'd say things are fixed at this point. commit 5cd2c5b6ad75c46d40118ac67c0c09d4e7930a65 - compiles and issue is no longer present. - ./configure --target-list=x86_64-softmmu && make clean && make && sudo x86_64-softmmu/qemu-syem-x86_64 -L pc-bios -hda /dev/null -m 4097
On Wed, Jan 05, 2011 at 01:04:51PM -0600, Ryan Harper wrote: > * Ryan Harper <ryanh@us.ibm.com> [2011-01-04 09:49]: > > * Aurelien Jarno <aurelien@aurel32.net> [2010-12-25 16:37]: > > > On Wed, Dec 08, 2010 at 04:27:45PM -0200, Luiz Capitulino wrote: > > > > On Wed, 08 Dec 2010 12:23:12 -0600 > > > > Anthony Liguori <aliguori@linux.vnet.ibm.com> wrote: > > > > > > > > > On 12/08/2010 12:01 PM, Luiz Capitulino wrote: > > > > > > Currently, x86_64-softmmu qemu segfaults when trying to use> 4095M memsize. > > > > > > This patch adds a simple check and error message (much like the 2047 limit on > > > > > > 32-bit hosts) on ram_size in the control path after we determine we're > > > > > > not using kvm > > > > > > > > > > > > Upstream qemu-kvm is affected if using the -no-kvm option; this patch address > > > > > > the segfault there as well. > > > > > > > > > > > > Signed-off-by: Ryan Harper<ryanh@us.ibm.com> > > > > > > Signed-off-by: Aurelien Jarno<aurelien@aurel32.net> > > > > > > --- > > > > > > NOTE: this patch was applied in the v0.12.x branch, but it seems it got > > > > > > lost for master > > > > > > > > > > > > > > > > No, it was intentional. We should fix the segv, this is not a known > > > > > limitation but rather a bug. > > > > > > > > A TCG bug, I presume? > > > > > > > > > > Do you have more details about this issue and how to reproduce it? > > > > At the time of the bug, it was something simple like: > > > > qemu-system-x86_64 -m 4097 -hda /dev/null > > > > we'd get an imediate segfault. As you say, I'm not seeing it now on > > current git; I'll see about bisecting to see if we did get a fix for the > > issue. > > I attempted to bisect, but there a couple commits around where the issue > was fixed that broke git bisect =( That narrowed it down to about 5 > commits to check. > > This the last git commit where I can reproduce the segfault with the > above test case (qemu invocation). > > commit 0aef4261ac0ec9089ade0e3a92f986cb4ba7317e > Author: Aurelien Jarno <aurelien@aurel32.net> > Date: Thu Mar 11 21:29:42 2010 +0100 > > target-ppc: fix evsrwu and evsrws (second try) > > Signed-off-by: Aurelien Jarno <aurelien@aurel32.net> > > > The next 4 commits don't compile so they are untest-able: > > commit 14f24e1465edc44b9b4d89fbbea66e06088154e1 > - fails to build with: > - ./configure --target-list=x86_64-softmmu && make clean && make > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': > /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': > /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > make[1]: *** [exec.o] Error 1 > make: *** [subdir-x86_64-softmmu] Error 2 > > commit 7bc7b099dfa38a856b1bc892c0f9f3d6fe28e170 > - fails to build with: > - ./configure --target-list=x86_64-softmmu && make clean && make > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': > /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': > /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > make[1]: *** [exec.o] Error 1 > make: *** [subdir-x86_64-softmmu] Error 2 > > commit b9f83121a13153536d886305414b540460c34508 > - fails to build with: > - ./configure --target-list=x86_64-softmmu && make clean && make > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': > /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': > /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > make[1]: *** [exec.o] Error 1 > make: *** [subdir-x86_64-softmmu] Error 2 > > commit 5270589032f450ae7c3448730855aa18ff68ccff > - fails to build with: > - ./configure --target-list=x86_64-softmmu && make clean && make > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_find_alloc': > /home/rharper/work/git/qemu/exec.c:341: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > /home/rharper/work/git/qemu/exec.c: In function 'phys_page_for_each': > /home/rharper/work/git/qemu/exec.c:1670: error: #error unsupported TARGET_PHYS_ADDR_SPACE_BITS > make[1]: *** [exec.o] Error 1 > make: *** [subdir-x86_64-softmmu] Error 2 > > > And this commit compiles and the test case no longer segfaults. So I'd > say things are fixed at this point. > > commit 5cd2c5b6ad75c46d40118ac67c0c09d4e7930a65 > - compiles and issue is no longer present. > - ./configure --target-list=x86_64-softmmu && make clean && make && > sudo x86_64-softmmu/qemu-syem-x86_64 -L pc-bios -hda /dev/null -m 4097 > It's more likely this commit which fixes the bug.
diff --git a/vl.c b/vl.c index 2dbb6db..bb9c21c 100644 --- a/vl.c +++ b/vl.c @@ -5792,6 +5792,12 @@ int main(int argc, char **argv, char **envp) fprintf(stderr, "failed to initialize KVM\n"); exit(1); } + } else { + /* without kvm enabled, we can only support 4095 MB RAM */ + if (ram_size > (4095UL << 20)) { + fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM can be simulated\n"); + exit(1); + } } if (qemu_init_main_loop()) {