Messages in this thread | | | Date | Mon, 21 Aug 2023 08:44:30 +0200 | Subject | Re: [PATCH] x86/sev: Make early_set_memory_decrypted() calls page aligned | From | "Gupta, Pankaj" <> |
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On 8/19/2023 1:34 AM, Steve Rutherford wrote: > early_set_memory_decrypted() assumes its parameters are page aligned. > Non-page aligned calls result in additional pages being marked as > decrypted via the encryption status hypercall, which results in > consistent corruption of pages during live migration. Live > migration requires accurate encryption status information to avoid > migrating pages from the wrong perspective. > > Fixes: 4716276184ec ("X86/KVM: Decrypt shared per-cpu variables when SEV is active") > Signed-off-by: Steve Rutherford <srutherford@google.com> > --- > arch/x86/kernel/kvm.c | 14 +++++++++++++- > 1 file changed, 13 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index 6a36db4f79fd..a0c072d3103c 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -419,7 +419,14 @@ static u64 kvm_steal_clock(int cpu) > > static inline void __set_percpu_decrypted(void *ptr, unsigned long size) > { > - early_set_memory_decrypted((unsigned long) ptr, size); > + /* > + * early_set_memory_decrypted() requires page aligned parameters, but > + * this function needs to handle ptrs offset into a page. > + */ > + unsigned long start = PAGE_ALIGN_DOWN((unsigned long) ptr); > + unsigned long end = (unsigned long) ptr + size; > + > + early_set_memory_decrypted(start, end - start); > } > > /* > @@ -438,6 +445,11 @@ static void __init sev_map_percpu_data(void) > return; > > for_each_possible_cpu(cpu) { > + /* > + * Calling __set_percpu_decrypted() for each per-cpu variable is > + * inefficent, since it may decrypt the same page multiple times. > + * That said, it avoids the need for more complicated logic. > + */ > __set_percpu_decrypted(&per_cpu(apf_reason, cpu), sizeof(apf_reason)); > __set_percpu_decrypted(&per_cpu(steal_time, cpu), sizeof(steal_time)); > __set_percpu_decrypted(&per_cpu(kvm_apic_eoi, cpu), sizeof(kvm_apic_eoi));
The fix looks correct to me.
Reviewed-by: Pankaj Gupta <pankaj.gupta@amd.com>
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