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Commit 6807cf65 authored by Juergen Gross's avatar Juergen Gross
Browse files

x86/xen: use capabilities instead of fake cpuid values for xsave 



When running as pv domain xen_cpuid() is being used instead of
native_cpuid(). In xen_cpuid() the xsave feature availability is
indicated by special casing the related cpuid leaf.

Instead of delivering fake cpuid values set or clear the cpu
capability bits for xsave instead.

Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarAndrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent e657fccb

arch/x86/xen/enlighten_pv.c

+30 −23
Original line number Diff line number Diff line
@@ -165,8 +165,6 @@ xen_running_on_version_or_later(unsigned int major, unsigned int minor) 
	return false;

}



static __read_mostly unsigned int cpuid_leaf1_ecx_mask = ~0;



static __read_mostly unsigned int cpuid_leaf5_ecx_val;

static __read_mostly unsigned int cpuid_leaf5_edx_val;
@@ -174,16 +172,12 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx, 
		      unsigned int *cx, unsigned int *dx)

{

	unsigned maskebx = ~0;

	unsigned maskecx = ~0;



	/*

	 * Mask out inconvenient features, to try and disable as many

	 * unsupported kernel subsystems as possible.

	 */

	switch (*ax) {

	case 1:

		maskecx = cpuid_leaf1_ecx_mask;

		break;



	case CPUID_MWAIT_LEAF:

		/* Synthesize the values.. */

		*ax = 0;
@@ -206,7 +200,6 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx, 
		: "0" (*ax), "2" (*cx));



	*bx &= maskebx;

	*cx &= maskecx;

}

STACK_FRAME_NON_STANDARD(xen_cpuid); /* XEN_EMULATE_PREFIX */
@@ -281,22 +274,29 @@ static bool __init xen_check_mwait(void) 
	return false;

#endif

}

static void __init xen_init_cpuid_mask(void)

{

	unsigned int ax, bx, cx, dx;

	unsigned int xsave_mask;



	ax = 1;

	cx = 0;

	cpuid(1, &ax, &bx, &cx, &dx);

static bool __init xen_check_xsave(void)

{

	unsigned int err, eax, edx;



	xsave_mask =

		(1 << (X86_FEATURE_XSAVE % 32)) |

		(1 << (X86_FEATURE_OSXSAVE % 32));

	/*

	 * Xen 4.0 and older accidentally leaked the host XSAVE flag into guest

	 * view, despite not being able to support guests using the

	 * functionality. Probe for the actual availability of XSAVE by seeing

	 * whether xgetbv executes successfully or raises #UD.

	 */

	asm volatile("1: .byte 0x0f,0x01,0xd0\n\t" /* xgetbv */

		     "xor %[err], %[err]\n"

		     "2:\n\t"

		     ".pushsection .fixup,\"ax\"\n\t"

		     "3: movl $1,%[err]\n\t"

		     "jmp 2b\n\t"

		     ".popsection\n\t"

		     _ASM_EXTABLE(1b, 3b)

		     : [err] "=r" (err), "=a" (eax), "=d" (edx)

		     : "c" (0));



	/* Xen will set CR4.OSXSAVE if supported and not disabled by force */

	if ((cx & xsave_mask) != xsave_mask)

		cpuid_leaf1_ecx_mask &= ~xsave_mask; /* disable XSAVE & OSXSAVE */

	return err == 0;

}



static void __init xen_init_capabilities(void)
@@ -316,6 +316,14 @@ static void __init xen_init_capabilities(void) 
		setup_force_cpu_cap(X86_FEATURE_MWAIT);

	else

		setup_clear_cpu_cap(X86_FEATURE_MWAIT);



	if (xen_check_xsave()) {

		setup_force_cpu_cap(X86_FEATURE_XSAVE);

		setup_force_cpu_cap(X86_FEATURE_OSXSAVE);

	} else {

		setup_clear_cpu_cap(X86_FEATURE_XSAVE);

		setup_clear_cpu_cap(X86_FEATURE_OSXSAVE);

	}

}



static void xen_set_debugreg(int reg, unsigned long val)
@@ -1308,7 +1316,6 @@ asmlinkage __visible void __init xen_start_kernel(void) 
	xen_setup_gdt(0);



	xen_init_irq_ops();

	xen_init_cpuid_mask();

	xen_init_capabilities();



#ifdef CONFIG_X86_LOCAL_APIC