On Fri, Aug 07, 2020 at 12:02:59PM +0200, Jürgen Groß wrote:

On 07.08.20 11:39, peterz@infradead.org wrote:

quoted

On Fri, Aug 07, 2020 at 10:38:23AM +0200, Juergen Gross wrote:

quoted

-# 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!
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