Re: [PATCH] KVM: PPC: paravirt: Avoid patching paravirt template

Scott Wood
2011-11-28T17:32:02Z

On 11/23/2011 04:05 AM, Liu Yu wrote:
> Currently we patch the whole code include paravirt template code.
> This doesn't lead into issue for now,
> but it makes some previlege instructions branch to paravirt code twice.

Ouch. This will do bad things to the scratch area.

> Signed-off-by: Liu Yu <yu.liu@freescale.com>
> ---
> arch/powerpc/kernel/kvm.c | 17 +++++++++++++++++
> 1 files changed, 17 insertions(+), 0 deletions(-)
>
> diff --git a/arch/powerpc/kernel/kvm.c b/arch/powerpc/kernel/kvm.c
> index 3953fbd..485748c 100644
> --- a/arch/powerpc/kernel/kvm.c
> +++ b/arch/powerpc/kernel/kvm.c
> @@ -171,6 +171,10 @@ static void kvm_patch_ins_mtmsrd(u32 *inst, u32 rt)
> if (!p)
> return;
>
> + if ((inst > kvm_emulate_mtmsrd) &&
> + (inst < kvm_emulate_mtmsrd + kvm_emulate_mtmsrd_len))
> + return;
> +
> /* Find out where we are and put everything there */
> distance_start = (ulong)p - (ulong)inst;
> next_inst = ((ulong)inst + 4);
> @@ -220,6 +224,11 @@ static void kvm_patch_ins_mtmsr(u32 *inst, u32 rt)
> int distance_end;
> ulong next_inst;
>
> + if ((inst > kvm_emulate_mtmsr) &&
> + (inst < kvm_emulate_mtmsr + kvm_emulate_mtmsr_len))
> + return;
> +
> +
> p = kvm_alloc(kvm_emulate_mtmsr_len * 4);
> if (!p)
> return;
> @@ -281,6 +290,10 @@ static void kvm_patch_ins_wrtee(u32 *inst, u32 rt, int imm_one)
> int distance_end;
> ulong next_inst;
>
> + if ((inst > kvm_emulate_wrtee) &&
> + (inst < kvm_emulate_wrtee + kvm_emulate_wrtee_len))
> + return;
> +
> p = kvm_alloc(kvm_emulate_wrtee_len * 4);
> if (!p)
> return;
> @@ -338,6 +351,10 @@ static void kvm_patch_ins_wrteei_0(u32 *inst)
> int distance_end;
> ulong next_inst;
>
> + if ((inst > kvm_emulate_wrteei_0) &&
> + (inst < kvm_emulate_wrteei_0 + kvm_emulate_wrteei_0_len))
> + return;
> +
> p = kvm_alloc(kvm_emulate_wrteei_0_len * 4);
> if (!p)
> return;

Instead of excluding only the template code for the instruction type
being patched, we should exclude the entire template region in the main
loop.

-Scott