Commit a1886b91 authored by Juergen Gross's avatar Juergen Gross
Browse files

xen/pv: refactor msr access functions to support safe and unsafe accesses 



Refactor and rename xen_read_msr_safe() and xen_write_msr_safe() to
support both cases of MSR accesses, safe ones and potentially GP-fault
generating ones.

This will prepare to no longer swallow GPs silently in xen_read_msr()
and xen_write_msr().

Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent f90d98bd

arch/x86/xen/enlighten_pv.c

+56 −19
Original line number Diff line number Diff line
@@ -916,14 +916,18 @@ static void xen_write_cr4(unsigned long cr4) 
	native_write_cr4(cr4);

}



static u64 xen_read_msr_safe(unsigned int msr, int *err)

static u64 xen_do_read_msr(unsigned int msr, int *err)

{

	u64 val;

	u64 val = 0;	/* Avoid uninitialized value for safe variant. */



	if (pmu_msr_read(msr, &val, err))

		return val;



	if (err)

		val = native_read_msr_safe(msr, err);

	else

		val = native_read_msr(msr);



	switch (msr) {

	case MSR_IA32_APICBASE:

		val &= ~X2APIC_ENABLE;
@@ -932,23 +936,39 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err) 
	return val;

}



static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)

static void set_seg(unsigned int which, unsigned int low, unsigned int high,

		    int *err)

{

	int ret;

	unsigned int which;

	u64 base;

	u64 base = ((u64)high << 32) | low;



	ret = 0;

	if (HYPERVISOR_set_segment_base(which, base) == 0)

		return;



	if (err)

		*err = -EIO;

	else

		WARN(1, "Xen set_segment_base(%u, %llx) failed\n", which, base);

}



/*

 * Support write_msr_safe() and write_msr() semantics.

 * With err == NULL write_msr() semantics are selected.

 * Supplying an err pointer requires err to be pre-initialized with 0.

 */

static void xen_do_write_msr(unsigned int msr, unsigned int low,

			     unsigned int high, int *err)

{

	switch (msr) {

	case MSR_FS_BASE:		which = SEGBASE_FS; goto set;

	case MSR_KERNEL_GS_BASE:	which = SEGBASE_GS_USER; goto set;

	case MSR_GS_BASE:		which = SEGBASE_GS_KERNEL; goto set;



	set:

		base = ((u64)high << 32) | low;

		if (HYPERVISOR_set_segment_base(which, base) != 0)

			ret = -EIO;

	case MSR_FS_BASE:

		set_seg(SEGBASE_FS, low, high, err);

		break;



	case MSR_KERNEL_GS_BASE:

		set_seg(SEGBASE_GS_USER, low, high, err);

		break;



	case MSR_GS_BASE:

		set_seg(SEGBASE_GS_KERNEL, low, high, err);

		break;



	case MSR_STAR:
@@ -964,11 +984,28 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high) 
		break;



	default:

		if (!pmu_msr_write(msr, low, high, &ret))

			ret = native_write_msr_safe(msr, low, high);

		if (!pmu_msr_write(msr, low, high, err)) {

			if (err)

				*err = native_write_msr_safe(msr, low, high);

			else

				native_write_msr(msr, low, high);

		}

	}

}



static u64 xen_read_msr_safe(unsigned int msr, int *err)

{

	return xen_do_read_msr(msr, err);

}



	return ret;

static int xen_write_msr_safe(unsigned int msr, unsigned int low,

			      unsigned int high)

{

	int err = 0;



	xen_do_write_msr(msr, low, high, &err);



	return err;

}



static u64 xen_read_msr(unsigned int msr)