Re: [PATCH v3 4/7] x86/paravirt: remove 32-bit support from PARAVIRT_XXL

From: peterz
Date: Fri Aug 07 2020 - 06:22:21 EST


On Fri, Aug 07, 2020 at 12:02:59PM +0200, Jürgen Groß wrote:
> On 07.08.20 11:39, peterz@xxxxxxxxxxxxx wrote:
> > On Fri, Aug 07, 2020 at 10:38:23AM +0200, Juergen Gross wrote:
> >
> > > -# else
> > > - const unsigned char cpu_iret[1];
> > > -# endif
> > > };
> > > static const struct patch_xxl patch_data_xxl = {
> > > @@ -42,7 +38,6 @@ static const struct patch_xxl patch_data_xxl = {
> > > .irq_save_fl = { 0x9c, 0x58 }, // pushf; pop %[re]ax
> > > .mmu_read_cr2 = { 0x0f, 0x20, 0xd0 }, // mov %cr2, %[re]ax
> > > .mmu_read_cr3 = { 0x0f, 0x20, 0xd8 }, // mov %cr3, %[re]ax
> > > -# ifdef CONFIG_X86_64
> > > .mmu_write_cr3 = { 0x0f, 0x22, 0xdf }, // mov %rdi, %cr3
> > > .irq_restore_fl = { 0x57, 0x9d }, // push %rdi; popfq
> > > .cpu_wbinvd = { 0x0f, 0x09 }, // wbinvd
> > > @@ -50,19 +45,11 @@ static const struct patch_xxl patch_data_xxl = {
> > > 0x48, 0x0f, 0x07 }, // swapgs; sysretq
> > > .cpu_swapgs = { 0x0f, 0x01, 0xf8 }, // swapgs
> > > .mov64 = { 0x48, 0x89, 0xf8 }, // mov %rdi, %rax
> > > -# else
> > > - .mmu_write_cr3 = { 0x0f, 0x22, 0xd8 }, // mov %eax, %cr3
> > > - .irq_restore_fl = { 0x50, 0x9d }, // push %eax; popf
> > > - .cpu_iret = { 0xcf }, // iret
> > > -# endif
> >
> > I was looking at x86_64 paravirt the other day and found we actually
> > have pv_ops.cpu.iret users there..
>
> On x86_64 we have (without PARAVIRT_XXL):
>
> #define INTERRUPT_RETURN jmp native_iret
>
> and with PARAVIRT_XXL this is basically a jmp *pv_ops.cpu.iret which
> will then be patched to either jmp native_iret or jmp xen_iret.

Ah, okay. Clearly I didn't look hard enough. Thanks!