This is a note to let you know that I've just added the patch titled KVM: x86: clflushopt should be treated as a no-op by emulation to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: kvm-x86-clflushopt-should-be-treated-as-a-no-op-by-emulation.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 51b958e5aeb1e18c00332e0b37c5d4e95a3eff84 Mon Sep 17 00:00:00 2001 From: David Edmondson <david.edmondson@xxxxxxxxxx> Date: Tue, 3 Nov 2020 12:04:00 +0000 Subject: KVM: x86: clflushopt should be treated as a no-op by emulation From: David Edmondson <david.edmondson@xxxxxxxxxx> commit 51b958e5aeb1e18c00332e0b37c5d4e95a3eff84 upstream. The instruction emulator ignores clflush instructions, yet fails to support clflushopt. Treat both similarly. Fixes: 13e457e0eebf ("KVM: x86: Emulator does not decode clflush well") Signed-off-by: David Edmondson <david.edmondson@xxxxxxxxxx> Message-Id: <20201103120400.240882-1-david.edmondson@xxxxxxxxxx> Reviewed-by: Joao Martins <joao.m.martins@xxxxxxxxxx> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/kvm/emulate.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -3922,6 +3922,12 @@ static int em_clflush(struct x86_emulate return X86EMUL_CONTINUE; } +static int em_clflushopt(struct x86_emulate_ctxt *ctxt) +{ + /* emulating clflushopt regardless of cpuid */ + return X86EMUL_CONTINUE; +} + static int em_movsxd(struct x86_emulate_ctxt *ctxt) { ctxt->dst.val = (s32) ctxt->src.val; @@ -4411,7 +4417,7 @@ static const struct opcode group11[] = { }; static const struct gprefix pfx_0f_ae_7 = { - I(SrcMem | ByteOp, em_clflush), N, N, N, + I(SrcMem | ByteOp, em_clflush), I(SrcMem | ByteOp, em_clflushopt), N, N, }; static const struct group_dual group15 = { { Patches currently in stable-queue which might be from david.edmondson@xxxxxxxxxx are queue-4.4/kvm-x86-clflushopt-should-be-treated-as-a-no-op-by-emulation.patch