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@xxxxxxxxxx>
---
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
--
Jazz is not dead. It just smells funny...
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