| Message ID | 20171122034221.647-1-aik@ozlabs.ru (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [RFC,kernel] KVM: PPC: Book3S PR: Fix WIMG handling under pHyp | expand |
On 22.11.17 04:42, Alexey Kardashevskiy wrote: > 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" added WIMG > bits preserving but it missed 2 special cases: > - a magic page in kvmppc_mmu_book3s_64_xlate() and > - guest real mode in kvmppc_handle_pagefault(). > > For these ptes WIMG were 0 and pHyp failed on these causing a guest to > stop in the very beginning at NIP=0x100 (due to bd9166ffe > "KVM: PPC: Book3S PR: Exit KVM on failed mapping"). > > This initializes WIMG to non-zero value HPTE_R_M. The value is chosen > as (0x192 & HPTE_R_WIMG); 0x192 is a magic value from > kvmppc_mmu_map_page(). > > Fixes: 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> > --- > > This indeed fixes PR KVM + VFIO under pHyp but selection of HPTE_R_M > is arguable. This does indeed fix the breakage we've seen: Tested-by: Ruediger Oertel <ro@suse.de> Alex
On Wed, 22 Nov 2017 14:42:21 +1100 Alexey Kardashevskiy <aik@ozlabs.ru> wrote: > 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" added WIMG > bits preserving but it missed 2 special cases: > - a magic page in kvmppc_mmu_book3s_64_xlate() and > - guest real mode in kvmppc_handle_pagefault(). > > For these ptes WIMG were 0 and pHyp failed on these causing a guest to > stop in the very beginning at NIP=0x100 (due to bd9166ffe > "KVM: PPC: Book3S PR: Exit KVM on failed mapping"). > > This initializes WIMG to non-zero value HPTE_R_M. The value is chosen > as (0x192 & HPTE_R_WIMG); 0x192 is a magic value from > kvmppc_mmu_map_page(). > > Fixes: 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> > --- > > This indeed fixes PR KVM + VFIO under pHyp but selection of HPTE_R_M > is arguable. > The initial page fault at 0x100 on machine startup causes H_ENTER to fail in pHyp with H_PARAMETER, as described in PAPR: The hypervisor checks that the WIMG bits within the PTE are appropriate for the physical page number else H_Parameter return. (For System Memory pages WIMG=0010, or, 1110 if the SAO option is enabled, and for IO pages WIMG=01**.) I'm not aware we care for SAO so HPTE_R_M looks like the only sensible choice, or I'm missing something ? Anyway, this patch allows to start a PR guest on PowerVM again. Reviewed-by: Greg Kurz <groug@kaod.org> and Tested-by: Greg Kurz <groug@kaod.org> > --- > arch/powerpc/kvm/book3s_64_mmu.c | 1 + > arch/powerpc/kvm/book3s_pr.c | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/arch/powerpc/kvm/book3s_64_mmu.c b/arch/powerpc/kvm/book3s_64_mmu.c > index 29ebe2f..a93d719 100644 > --- a/arch/powerpc/kvm/book3s_64_mmu.c > +++ b/arch/powerpc/kvm/book3s_64_mmu.c > @@ -235,6 +235,7 @@ static int kvmppc_mmu_book3s_64_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, > gpte->may_read = true; > gpte->may_write = true; > gpte->page_size = MMU_PAGE_4K; > + gpte->wimg = HPTE_R_M; > > return 0; > } > diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c > index 69a0944..0152efe 100644 > --- a/arch/powerpc/kvm/book3s_pr.c > +++ b/arch/powerpc/kvm/book3s_pr.c > @@ -557,6 +557,7 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu, > pte.eaddr = eaddr; > pte.vpage = eaddr >> 12; > pte.page_size = MMU_PAGE_64K; > + pte.wimg = HPTE_R_M; > } > > switch (kvmppc_get_msr(vcpu) & (MSR_DR|MSR_IR)) {
On 24.11.17 00:33, Greg Kurz wrote: > On Wed, 22 Nov 2017 14:42:21 +1100 > Alexey Kardashevskiy <aik@ozlabs.ru> wrote: > >> 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" added WIMG >> bits preserving but it missed 2 special cases: >> - a magic page in kvmppc_mmu_book3s_64_xlate() and >> - guest real mode in kvmppc_handle_pagefault(). >> >> For these ptes WIMG were 0 and pHyp failed on these causing a guest to >> stop in the very beginning at NIP=0x100 (due to bd9166ffe >> "KVM: PPC: Book3S PR: Exit KVM on failed mapping"). >> >> This initializes WIMG to non-zero value HPTE_R_M. The value is chosen >> as (0x192 & HPTE_R_WIMG); 0x192 is a magic value from >> kvmppc_mmu_map_page(). >> >> Fixes: 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" >> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> >> --- >> >> This indeed fixes PR KVM + VFIO under pHyp but selection of HPTE_R_M >> is arguable. >> > > The initial page fault at 0x100 on machine startup causes H_ENTER to fail in > pHyp with H_PARAMETER, as described in PAPR: > > The hypervisor checks that the WIMG bits within the PTE are appropriate for the > physical page number else H_Parameter return. (For System Memory pages WIMG=0010, > or, 1110 if the SAO option is enabled, and for IO pages WIMG=01**.) > > I'm not aware we care for SAO so HPTE_R_M looks like the only sensible choice, > or I'm missing something ? > > Anyway, this patch allows to start a PR guest on PowerVM again. > > Reviewed-by: Greg Kurz <groug@kaod.org> > > and > > Tested-by: Greg Kurz <groug@kaod.org> So doesn't that mean we should pick it up, mark it CC stable and push it upstream? Alex
Paul, I saw comments about the commit log but did this go to any tree eventually? On 22/11/17 14:42, Alexey Kardashevskiy wrote: > 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" added WIMG > bits preserving but it missed 2 special cases: > - a magic page in kvmppc_mmu_book3s_64_xlate() and > - guest real mode in kvmppc_handle_pagefault(). > > For these ptes WIMG were 0 and pHyp failed on these causing a guest to > stop in the very beginning at NIP=0x100 (due to bd9166ffe > "KVM: PPC: Book3S PR: Exit KVM on failed mapping"). > > This initializes WIMG to non-zero value HPTE_R_M. The value is chosen > as (0x192 & HPTE_R_WIMG); 0x192 is a magic value from > kvmppc_mmu_map_page(). > > Fixes: 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> > --- > > This indeed fixes PR KVM + VFIO under pHyp but selection of HPTE_R_M > is arguable. > > --- > arch/powerpc/kvm/book3s_64_mmu.c | 1 + > arch/powerpc/kvm/book3s_pr.c | 1 + > 2 files changed, 2 insertions(+) > > diff --git a/arch/powerpc/kvm/book3s_64_mmu.c b/arch/powerpc/kvm/book3s_64_mmu.c > index 29ebe2f..a93d719 100644 > --- a/arch/powerpc/kvm/book3s_64_mmu.c > +++ b/arch/powerpc/kvm/book3s_64_mmu.c > @@ -235,6 +235,7 @@ static int kvmppc_mmu_book3s_64_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, > gpte->may_read = true; > gpte->may_write = true; > gpte->page_size = MMU_PAGE_4K; > + gpte->wimg = HPTE_R_M; > > return 0; > } > diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c > index 69a0944..0152efe 100644 > --- a/arch/powerpc/kvm/book3s_pr.c > +++ b/arch/powerpc/kvm/book3s_pr.c > @@ -557,6 +557,7 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu, > pte.eaddr = eaddr; > pte.vpage = eaddr >> 12; > pte.page_size = MMU_PAGE_64K; > + pte.wimg = HPTE_R_M; > } > > switch (kvmppc_get_msr(vcpu) & (MSR_DR|MSR_IR)) { >
On Wed, Nov 22, 2017 at 02:42:21PM +1100, Alexey Kardashevskiy wrote: > 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" added WIMG > bits preserving but it missed 2 special cases: > - a magic page in kvmppc_mmu_book3s_64_xlate() and > - guest real mode in kvmppc_handle_pagefault(). > > For these ptes WIMG were 0 and pHyp failed on these causing a guest to > stop in the very beginning at NIP=0x100 (due to bd9166ffe > "KVM: PPC: Book3S PR: Exit KVM on failed mapping"). > > This initializes WIMG to non-zero value HPTE_R_M. The value is chosen > as (0x192 & HPTE_R_WIMG); 0x192 is a magic value from > kvmppc_mmu_map_page(). > > Fixes: 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" > Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> Thanks, applied to my kvm-ppc-fixes branch, with an updated commit message, fixes: tag, and cc:stable@vger.kernel.org. Paul.
diff --git a/arch/powerpc/kvm/book3s_64_mmu.c b/arch/powerpc/kvm/book3s_64_mmu.c index 29ebe2f..a93d719 100644 --- a/arch/powerpc/kvm/book3s_64_mmu.c +++ b/arch/powerpc/kvm/book3s_64_mmu.c @@ -235,6 +235,7 @@ static int kvmppc_mmu_book3s_64_xlate(struct kvm_vcpu *vcpu, gva_t eaddr, gpte->may_read = true; gpte->may_write = true; gpte->page_size = MMU_PAGE_4K; + gpte->wimg = HPTE_R_M; return 0; } diff --git a/arch/powerpc/kvm/book3s_pr.c b/arch/powerpc/kvm/book3s_pr.c index 69a0944..0152efe 100644 --- a/arch/powerpc/kvm/book3s_pr.c +++ b/arch/powerpc/kvm/book3s_pr.c @@ -557,6 +557,7 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu, pte.eaddr = eaddr; pte.vpage = eaddr >> 12; pte.page_size = MMU_PAGE_64K; + pte.wimg = HPTE_R_M; } switch (kvmppc_get_msr(vcpu) & (MSR_DR|MSR_IR)) {
96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" added WIMG bits preserving but it missed 2 special cases: - a magic page in kvmppc_mmu_book3s_64_xlate() and - guest real mode in kvmppc_handle_pagefault(). For these ptes WIMG were 0 and pHyp failed on these causing a guest to stop in the very beginning at NIP=0x100 (due to bd9166ffe "KVM: PPC: Book3S PR: Exit KVM on failed mapping"). This initializes WIMG to non-zero value HPTE_R_M. The value is chosen as (0x192 & HPTE_R_WIMG); 0x192 is a magic value from kvmppc_mmu_map_page(). Fixes: 96df226 "KVM: PPC: Book3S PR: Preserve storage control bits" Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru> --- This indeed fixes PR KVM + VFIO under pHyp but selection of HPTE_R_M is arguable. --- arch/powerpc/kvm/book3s_64_mmu.c | 1 + arch/powerpc/kvm/book3s_pr.c | 1 + 2 files changed, 2 insertions(+)