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Re: [Qemu-devel] [PATCH v4 1/2] i386: Add Intel Processor Trace feature
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH v4 1/2] i386: Add Intel Processor Trace feature support |
Date: |
Fri, 9 Mar 2018 16:10:48 -0300 |
User-agent: |
Mutt/1.9.2 (2017-12-15) |
On Mon, Mar 05, 2018 at 12:48:35AM +0800, Luwei Kang wrote:
> From: Chao Peng <address@hidden>
>
> Expose Intel Processor Trace feature to guest.
>
> To make Intel PT live migration safe and get same CPUID information
> with same CPU model on diffrent host. CPUID[14] is constant in this
> patch. Intel PT use EPT is first supported in IceLake, the CPUID[14]
> get on this machine as default value. Intel PT would be disabled
> if any machine don't support this minial feature list.
>
> Signed-off-by: Chao Peng <address@hidden>
> Signed-off-by: Luwei Kang <address@hidden>
> ---
> From V3:
> - fix some typo;
> - add some comments and safty check.
>
> ---
> target/i386/cpu.c | 78
> +++++++++++++++++++++++++++++++++++++++++++++++++++++--
> target/i386/cpu.h | 1 +
> target/i386/kvm.c | 23 ++++++++++++++++
> 3 files changed, 100 insertions(+), 2 deletions(-)
>
> diff --git a/target/i386/cpu.c b/target/i386/cpu.c
> index b5e431e..24e1693 100644
> --- a/target/i386/cpu.c
> +++ b/target/i386/cpu.c
> @@ -173,7 +173,32 @@
> #define L2_ITLB_4K_ASSOC 4
> #define L2_ITLB_4K_ENTRIES 512
>
> -
> +/* CPUID Leaf 0x14 constants: */
> +#define INTEL_PT_MAX_SUBLEAF 0x1
> +/*
> + * bit[00]: IA32_RTIT_CTL.CR3 filter can be set to 1 and IA32_RTIT_CR3_MATCH
> + * MSR can be accessed;
> + * bit[01]: Support Configurable PSB and Cycle-Accurate Mode;
> + * bit[02]: Support IP Filtering, TraceStop filtering, and preservation
> + * of Intel PT MSRs across warm reset;
> + * bit[03]: Support MTC timing packet and suppression of COFI-based packets;
> + */
> +#define INTEL_PT_MINIMAL_EBX 0xf
Thanks! I didn't expect a detailed description of each bit. I
thought that just adding macros for each bit instead of
hardcoding 0xf would be enough.
But after reading the docs, I understand it could be difficult to
choose a macro name for something like "support of IP Filtering,
TraceStop filtering, and preservation of Intel PT MSRs across
warm reset", so this description looks like the best we can do.
:)
I only see a problem below:
> +/*
> + * bit[00]: Tracing can be enabled with IA32_RTIT_CTL.ToPA = 1 and
> + * IA32_RTIT_OUTPUT_BASE and IA32_RTIT_OUTPUT_MASK_PTRS MSRs can be
> + * accessed;
> + * bit[01]: ToPA tables can hold any number of output entries, up to the
> + * maximum allowed by the MaskOrTableOffset field of
> + * IA32_RTIT_OUTPUT_MASK_PTRS;
> + * bit[02]: Support Single-Range Output scheme;
> + */
> +#define INTEL_PT_MINIMAL_ECX 0x7
> +#define INTEL_PT_ADDR_RANGES_NUM 0x2 /* Number of configurable address
> ranges */
> +#define INTEL_PT_ADDR_RANGES_NUM_MASK 0x3
> +#define INTEL_PT_MTC_BITMAP (0x0249 << 16) /* Support ART(0,3,6,9) */
> +#define INTEL_PT_CYCLE_BITMAP 0x1fff /* Support 0,2^(0~11) */
> +#define INTEL_PT_PSB_BITMAP (0x003f << 16) /* Support
> 2K,4K,8K,16K,32K,64K */
>
> static void x86_cpu_vendor_words2str(char *dst, uint32_t vendor1,
> uint32_t vendor2, uint32_t vendor3)
[...]
> @@ -4083,6 +4129,34 @@ static int x86_cpu_filter_features(X86CPU *cpu)
> }
> }
>
> + if ((env->features[FEAT_7_0_EBX] & CPUID_7_0_EBX_INTEL_PT) &&
> + kvm_enabled()) {
> + KVMState *s = CPU(cpu)->kvm_state;
> + uint32_t eax_0 = kvm_arch_get_supported_cpuid(s, 0x14, 0, R_EAX);
> + uint32_t ebx_0 = kvm_arch_get_supported_cpuid(s, 0x14, 0, R_EBX);
> + uint32_t ecx_0 = kvm_arch_get_supported_cpuid(s, 0x14, 0, R_ECX);
> + uint32_t eax_1 = kvm_arch_get_supported_cpuid(s, 0x14, 1, R_EAX);
> + uint32_t ebx_1 = kvm_arch_get_supported_cpuid(s, 0x14, 1, R_EBX);
> +
> + if (!eax_0 ||
> + ((ebx_0 & INTEL_PT_MINIMAL_EBX) != INTEL_PT_MINIMAL_EBX) ||
> + ((ecx_0 & INTEL_PT_MINIMAL_ECX) != INTEL_PT_MINIMAL_ECX) ||
> + ((eax_1 & INTEL_PT_MTC_BITMAP) != INTEL_PT_MTC_BITMAP) ||
> + ((eax_1 & INTEL_PT_ADDR_RANGES_NUM_MASK) <
> + INTEL_PT_ADDR_RANGES_NUM) ||
> + ((ebx_1 & (INTEL_PT_PSB_BITMAP | INTEL_PT_CYCLE_BITMAP)) !=
> + (INTEL_PT_PSB_BITMAP | INTEL_PT_CYCLE_BITMAP))) {
I still don't see a check to ensure the host has bit 31 on ecx_0
set to 0, as I mentioned when reviewing v3.
The rest of the patch looks good.
> + /*
> + * Processor Trace capabilities aren't configurable, so if the
> + * host can't emulate the capabilities we report on
> + * cpu_x86_cpuid(), intel-pt can't be enabled on the current
> host.
> + */
> + env->features[FEAT_7_0_EBX] &= ~CPUID_7_0_EBX_INTEL_PT;
> + cpu->filtered_features[FEAT_7_0_EBX] |= CPUID_7_0_EBX_INTEL_PT;
> + rv = 1;
> + }
> + }
> +
> return rv;
> }
>
[...]
--
Eduardo