| Message ID | 20200930221239.488744-1-thomas.tai@oracle.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: Fixes ARM VM hangs at boot | expand |
Hi Thomas, On 2020-09-30 23:12, Thomas Tai wrote: > When using the latest kernel v5.9-rc7 on an ARM server, VMs could > hang at boot with no output. The commit a0e50aa3f4a8 removed > asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)), > it looks like isb is still needed for non > ARM64_WORKAROUND_SPECULATIVE_AT host when switching to guest. Is that on an eMAG system, by any chance? > > The code fragment for the original patch: > - /* __load_guest_stage2() includes an ISB for the workaround. */ > - __load_guest_stage2(kvm); > - asm(ALTERNATIVE("isb", "nop", > ARM64_WORKAROUND_SPECULATIVE_AT)); > + __load_guest_stage2(mmu); > > The code should have been: > - /* __load_guest_stage2() includes an ISB for the workaround. */ > - __load_guest_stage2(kvm); > - asm(ALTERNATIVE("isb", "nop", > ARM64_WORKAROUND_SPECULATIVE_AT)); > + __load_guest_stage2(mmu); > + asm(ALTERNATIVE("isb", "nop", > ARM64_WORKAROUND_SPECULATIVE_AT)); > ie, the workaround is still needed. > > Fixes: a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data > from > struct kvm") > > Signed-off-by: Thomas Tai <thomas.tai@oracle.com> > --- > arch/arm64/kvm/hyp/nvhe/tlb.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c > b/arch/arm64/kvm/hyp/nvhe/tlb.c > index 69eae60..536496e 100644 > --- a/arch/arm64/kvm/hyp/nvhe/tlb.c > +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c > @@ -32,6 +32,7 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu > *mmu, > } > > __load_guest_stage2(mmu); > + asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); > } > > static void __tlb_switch_to_host(struct tlb_inv_context *cxt) Ouch. I remember fixing this a while ago, but somehow dropped it after applying it and *not* merging it... Thanks a lot for the heads up! M. [1] https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/pre-nv-5.9
On 2020-10-01 4:30 a.m., Marc Zyngier wrote: > Hi Thomas, > > On 2020-09-30 23:12, Thomas Tai wrote: >> When using the latest kernel v5.9-rc7 on an ARM server, VMs could >> hang at boot with no output. The commit a0e50aa3f4a8 removed >> asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)), >> it looks like isb is still needed for non >> ARM64_WORKAROUND_SPECULATIVE_AT host when switching to guest. > > Is that on an eMAG system, by any chance? Hi Marc, Yes, it is indeed an eMAG system. > >> >> The code fragment for the original patch: >> - /* __load_guest_stage2() includes an ISB for the workaround. */ >> - __load_guest_stage2(kvm); >> - asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); >> + __load_guest_stage2(mmu); >> >> The code should have been: >> - /* __load_guest_stage2() includes an ISB for the workaround. */ >> - __load_guest_stage2(kvm); >> - asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); >> + __load_guest_stage2(mmu); >> + asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); >> ie, the workaround is still needed. >> >> Fixes: a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data from >> struct kvm") >> >> Signed-off-by: Thomas Tai <thomas.tai@oracle.com> >> --- >> arch/arm64/kvm/hyp/nvhe/tlb.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c >> b/arch/arm64/kvm/hyp/nvhe/tlb.c >> index 69eae60..536496e 100644 >> --- a/arch/arm64/kvm/hyp/nvhe/tlb.c >> +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c >> @@ -32,6 +32,7 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu >> *mmu, >> } >> >> __load_guest_stage2(mmu); >> + asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); >> } >> >> static void __tlb_switch_to_host(struct tlb_inv_context *cxt) > > Ouch. I remember fixing this a while ago, but somehow dropped it > after applying it and *not* merging it... > > Thanks a lot for the heads up! > > M. > > [1] > https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/pre-nv-5.9 Good to know you have the fix. Thank you, Thomas >
diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c b/arch/arm64/kvm/hyp/nvhe/tlb.c index 69eae60..536496e 100644 --- a/arch/arm64/kvm/hyp/nvhe/tlb.c +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c @@ -32,6 +32,7 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu *mmu, } __load_guest_stage2(mmu); + asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); } static void __tlb_switch_to_host(struct tlb_inv_context *cxt)
When using the latest kernel v5.9-rc7 on an ARM server, VMs could hang at boot with no output. The commit a0e50aa3f4a8 removed asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)), it looks like isb is still needed for non ARM64_WORKAROUND_SPECULATIVE_AT host when switching to guest. The code fragment for the original patch: - /* __load_guest_stage2() includes an ISB for the workaround. */ - __load_guest_stage2(kvm); - asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); + __load_guest_stage2(mmu); The code should have been: - /* __load_guest_stage2() includes an ISB for the workaround. */ - __load_guest_stage2(kvm); - asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); + __load_guest_stage2(mmu); + asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)); ie, the workaround is still needed. Fixes: a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data from struct kvm") Signed-off-by: Thomas Tai <thomas.tai@oracle.com> --- arch/arm64/kvm/hyp/nvhe/tlb.c | 1 + 1 file changed, 1 insertion(+)