| Message ID | 1259241800-2810-6-git-send-email-agraf@suse.de |
|---|---|
| State | New |
| Headers | show |
On Thu, Nov 26, 2009 at 02:23:14PM +0100, Alexander Graf wrote: > KVM on S390x requires the virtual address space of the guest's RAM to be > within the first 256GB. > While I have no problem with this patch, I am curious to know the reason of this. No need to change anything in the patch. > The general direction I'd like to see KVM on S390 move is that this requirement > is losened, but for now that's what we're stuck with. > > So let's just hack up qemu_ram_alloc until KVM behaves nicely :-). > > Signed-off-by: Alexander Graf <agraf@suse.de> > --- > exec.c | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/exec.c b/exec.c > index 076d26b..59150d0 100644 > --- a/exec.c > +++ b/exec.c > @@ -2411,7 +2411,13 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size) > size = TARGET_PAGE_ALIGN(size); > new_block = qemu_malloc(sizeof(*new_block)); > > +#if defined(TARGET_S390) && defined(CONFIG_KVM) > + /* XXX S390 KVM requires the topmost vma of the RAM to be < 256GB */ > + new_block->host = mmap(0x1000000, size, PROT_EXEC|PROT_READ|PROT_WRITE, > + MAP_SHARED | MAP_ANONYMOUS, -1, 0); > +#else > new_block->host = qemu_vmalloc(size); > +#endif > #ifdef MADV_MERGEABLE > madvise(new_block->host, size, MADV_MERGEABLE); > #endif > -- > 1.6.0.2 > > > >
On 30.11.2009, at 19:18, Aurelien Jarno wrote: > On Thu, Nov 26, 2009 at 02:23:14PM +0100, Alexander Graf wrote: >> KVM on S390x requires the virtual address space of the guest's RAM to be >> within the first 256GB. >> > > While I have no problem with this patch, I am curious to know the reason > of this. No need to change anything in the patch. For the technical reason I hope Carsten can provide some insight. As for the implementation reason - S390 KVM (the kernel part) doesn't do memslots properly :-). Alex
Alexander Graf wrote: > For the technical reason I hope Carsten can provide some insight. > As for the implementation reason - S390 KVM (the kernel part) doesn't do memslots properly :-). I'm sorry, I cannot comment on that :-(.
diff --git a/exec.c b/exec.c index 076d26b..59150d0 100644 --- a/exec.c +++ b/exec.c @@ -2411,7 +2411,13 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size) size = TARGET_PAGE_ALIGN(size); new_block = qemu_malloc(sizeof(*new_block)); +#if defined(TARGET_S390) && defined(CONFIG_KVM) + /* XXX S390 KVM requires the topmost vma of the RAM to be < 256GB */ + new_block->host = mmap(0x1000000, size, PROT_EXEC|PROT_READ|PROT_WRITE, + MAP_SHARED | MAP_ANONYMOUS, -1, 0); +#else new_block->host = qemu_vmalloc(size); +#endif #ifdef MADV_MERGEABLE madvise(new_block->host, size, MADV_MERGEABLE); #endif
KVM on S390x requires the virtual address space of the guest's RAM to be within the first 256GB. The general direction I'd like to see KVM on S390 move is that this requirement is losened, but for now that's what we're stuck with. So let's just hack up qemu_ram_alloc until KVM behaves nicely :-). Signed-off-by: Alexander Graf <agraf@suse.de> --- exec.c | 6 ++++++ 1 files changed, 6 insertions(+), 0 deletions(-)