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    Subject[RFC PATCH 66/73] x86/pvm: Use new cpu feature to describe XENPV and PVM
    Date
    From: Hou Wenlong <houwenlong.hwl@antgroup.com>

    Some PVOPS are patched as the native version directly if the guest is
    not a XENPV guest. However, this approach will not work after
    introducing a PVM guest. To address this, use a new CPU feature to
    describe XENPV and PVM, and ensure that those PVOPS are patched only
    when it is not a paravirtual guest.

    Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
    Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
    ---
    arch/x86/entry/entry_64.S | 5 ++---
    arch/x86/include/asm/cpufeatures.h | 1 +
    arch/x86/include/asm/paravirt.h | 14 +++++++-------
    arch/x86/kernel/pvm.c | 1 +
    arch/x86/xen/enlighten_pv.c | 1 +
    5 files changed, 12 insertions(+), 10 deletions(-)

    diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
    index fe12605b3c05..6b41a1837698 100644
    --- a/arch/x86/entry/entry_64.S
    +++ b/arch/x86/entry/entry_64.S
    @@ -127,9 +127,8 @@ SYM_INNER_LABEL(entry_SYSCALL_64_after_hwframe, SYM_L_GLOBAL)
    * In the PVM guest case we must use eretu synthetic instruction.
    */

    - ALTERNATIVE_2 "testb %al, %al; jz swapgs_restore_regs_and_return_to_usermode", \
    - "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_XENPV, \
    - "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_KVM_PVM_GUEST
    + ALTERNATIVE "testb %al, %al; jz swapgs_restore_regs_and_return_to_usermode", \
    + "jmp swapgs_restore_regs_and_return_to_usermode", X86_FEATURE_PV_GUEST

    /*
    * We win! This label is here just for ease of understanding
    diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
    index e17e72f13423..72ef58a2db19 100644
    --- a/arch/x86/include/asm/cpufeatures.h
    +++ b/arch/x86/include/asm/cpufeatures.h
    @@ -238,6 +238,7 @@
    #define X86_FEATURE_VCPUPREEMPT ( 8*32+21) /* "" PV vcpu_is_preempted function */
    #define X86_FEATURE_TDX_GUEST ( 8*32+22) /* Intel Trust Domain Extensions Guest */
    #define X86_FEATURE_KVM_PVM_GUEST ( 8*32+23) /* KVM Pagetable-based Virtual Machine guest */
    +#define X86_FEATURE_PV_GUEST ( 8*32+24) /* "" Paravirtual guest */

    /* Intel-defined CPU features, CPUID level 0x00000007:0 (EBX), word 9 */
    #define X86_FEATURE_FSGSBASE ( 9*32+ 0) /* RDFSBASE, WRFSBASE, RDGSBASE, WRGSBASE instructions*/
    diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
    index deaee9ec575e..a864ee481ca2 100644
    --- a/arch/x86/include/asm/paravirt.h
    +++ b/arch/x86/include/asm/paravirt.h
    @@ -143,7 +143,7 @@ static __always_inline unsigned long read_cr2(void)
    {
    return PVOP_ALT_CALLEE0(unsigned long, mmu.read_cr2,
    "mov %%cr2, %%rax;",
    - ALT_NOT(X86_FEATURE_XENPV));
    + ALT_NOT(X86_FEATURE_PV_GUEST));
    }

    static __always_inline void write_cr2(unsigned long x)
    @@ -154,13 +154,13 @@ static __always_inline void write_cr2(unsigned long x)
    static inline unsigned long __read_cr3(void)
    {
    return PVOP_ALT_CALL0(unsigned long, mmu.read_cr3,
    - "mov %%cr3, %%rax;", ALT_NOT(X86_FEATURE_XENPV));
    + "mov %%cr3, %%rax;", ALT_NOT(X86_FEATURE_PV_GUEST));
    }

    static inline void write_cr3(unsigned long x)
    {
    PVOP_ALT_VCALL1(mmu.write_cr3, x,
    - "mov %%rdi, %%cr3", ALT_NOT(X86_FEATURE_XENPV));
    + "mov %%rdi, %%cr3", ALT_NOT(X86_FEATURE_PV_GUEST));
    }

    static inline void __write_cr4(unsigned long x)
    @@ -694,17 +694,17 @@ bool __raw_callee_save___native_vcpu_is_preempted(long cpu);
    static __always_inline unsigned long arch_local_save_flags(void)
    {
    return PVOP_ALT_CALLEE0(unsigned long, irq.save_fl, "pushf; pop %%rax;",
    - ALT_NOT(X86_FEATURE_XENPV));
    + ALT_NOT(X86_FEATURE_PV_GUEST));
    }

    static __always_inline void arch_local_irq_disable(void)
    {
    - PVOP_ALT_VCALLEE0(irq.irq_disable, "cli;", ALT_NOT(X86_FEATURE_XENPV));
    + PVOP_ALT_VCALLEE0(irq.irq_disable, "cli;", ALT_NOT(X86_FEATURE_PV_GUEST));
    }

    static __always_inline void arch_local_irq_enable(void)
    {
    - PVOP_ALT_VCALLEE0(irq.irq_enable, "sti;", ALT_NOT(X86_FEATURE_XENPV));
    + PVOP_ALT_VCALLEE0(irq.irq_enable, "sti;", ALT_NOT(X86_FEATURE_PV_GUEST));
    }

    static __always_inline unsigned long arch_local_irq_save(void)
    @@ -776,7 +776,7 @@ void native_pv_lock_init(void) __init;
    .endm

    #define SAVE_FLAGS ALTERNATIVE "PARA_IRQ_save_fl;", "pushf; pop %rax;", \
    - ALT_NOT(X86_FEATURE_XENPV)
    + ALT_NOT(X86_FEATURE_PV_GUEST)
    #endif
    #endif /* CONFIG_PARAVIRT_XXL */
    #endif /* CONFIG_X86_64 */
    diff --git a/arch/x86/kernel/pvm.c b/arch/x86/kernel/pvm.c
    index c38e46a96ad3..d39550a8159f 100644
    --- a/arch/x86/kernel/pvm.c
    +++ b/arch/x86/kernel/pvm.c
    @@ -300,6 +300,7 @@ void __init pvm_early_setup(void)
    return;

    setup_force_cpu_cap(X86_FEATURE_KVM_PVM_GUEST);
    + setup_force_cpu_cap(X86_FEATURE_PV_GUEST);

    wrmsrl(MSR_PVM_VCPU_STRUCT, __pa(this_cpu_ptr(&pvm_vcpu_struct)));
    wrmsrl(MSR_PVM_EVENT_ENTRY, (unsigned long)(void *)pvm_early_kernel_event_entry - 256);
    diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
    index aeb33e0a3f76..c56483051528 100644
    --- a/arch/x86/xen/enlighten_pv.c
    +++ b/arch/x86/xen/enlighten_pv.c
    @@ -335,6 +335,7 @@ static bool __init xen_check_xsave(void)
    static void __init xen_init_capabilities(void)
    {
    setup_force_cpu_cap(X86_FEATURE_XENPV);
    + setup_force_cpu_cap(X86_FEATURE_PV_GUEST);
    setup_clear_cpu_cap(X86_FEATURE_DCA);
    setup_clear_cpu_cap(X86_FEATURE_APERFMPERF);
    setup_clear_cpu_cap(X86_FEATURE_MTRR);
    --
    2.19.1.6.gb485710b

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