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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: Juergen Gross <jgross@suse.com> Reviewed-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Juergen Gross <jgross@suse.com>
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1 changed files with 55 additions and 18 deletions
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@ -916,14 +916,18 @@ static void xen_write_cr4(unsigned long cr4)
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native_write_cr4(cr4);
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}
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static u64 xen_read_msr_safe(unsigned int msr, int *err)
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static u64 xen_do_read_msr(unsigned int msr, int *err)
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{
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u64 val;
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u64 val = 0; /* Avoid uninitialized value for safe variant. */
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if (pmu_msr_read(msr, &val, err))
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return val;
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val = native_read_msr_safe(msr, err);
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if (err)
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val = native_read_msr_safe(msr, err);
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else
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val = native_read_msr(msr);
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switch (msr) {
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case MSR_IA32_APICBASE:
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val &= ~X2APIC_ENABLE;
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@ -932,23 +936,39 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err)
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return val;
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}
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static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
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static void set_seg(unsigned int which, unsigned int low, unsigned int high,
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int *err)
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{
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int ret;
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unsigned int which;
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u64 base;
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u64 base = ((u64)high << 32) | low;
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ret = 0;
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if (HYPERVISOR_set_segment_base(which, base) == 0)
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return;
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if (err)
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*err = -EIO;
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else
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WARN(1, "Xen set_segment_base(%u, %llx) failed\n", which, base);
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}
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/*
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* Support write_msr_safe() and write_msr() semantics.
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* With err == NULL write_msr() semantics are selected.
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* Supplying an err pointer requires err to be pre-initialized with 0.
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*/
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static void xen_do_write_msr(unsigned int msr, unsigned int low,
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unsigned int high, int *err)
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{
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switch (msr) {
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case MSR_FS_BASE: which = SEGBASE_FS; goto set;
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case MSR_KERNEL_GS_BASE: which = SEGBASE_GS_USER; goto set;
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case MSR_GS_BASE: which = SEGBASE_GS_KERNEL; goto set;
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case MSR_FS_BASE:
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set_seg(SEGBASE_FS, low, high, err);
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break;
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set:
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base = ((u64)high << 32) | low;
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if (HYPERVISOR_set_segment_base(which, base) != 0)
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ret = -EIO;
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case MSR_KERNEL_GS_BASE:
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set_seg(SEGBASE_GS_USER, low, high, err);
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break;
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case MSR_GS_BASE:
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set_seg(SEGBASE_GS_KERNEL, low, high, err);
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break;
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case MSR_STAR:
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@ -964,11 +984,28 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
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break;
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default:
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if (!pmu_msr_write(msr, low, high, &ret))
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ret = native_write_msr_safe(msr, low, high);
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if (!pmu_msr_write(msr, low, high, err)) {
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if (err)
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*err = native_write_msr_safe(msr, low, high);
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else
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native_write_msr(msr, low, high);
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}
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}
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}
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return ret;
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static u64 xen_read_msr_safe(unsigned int msr, int *err)
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{
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return xen_do_read_msr(msr, err);
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}
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static int xen_write_msr_safe(unsigned int msr, unsigned int low,
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unsigned int high)
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{
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int err = 0;
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xen_do_write_msr(msr, low, high, &err);
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return err;
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}
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static u64 xen_read_msr(unsigned int msr)
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