From: Juergen Gross <jgross@suse.com>
To: xen-devel@lists.xenproject.org, x86@kernel.org,
linux-kernel@vger.kernel.org
Cc: Juergen Gross <jgross@suse.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: [PATCH 2/3] xen/pv: refactor msr access functions to support safe and unsafe accesses
Date: Mon, 26 Sep 2022 16:18:48 +0200 [thread overview]
Message-ID: <20220926141849.21805-3-jgross@suse.com> (raw)
In-Reply-To: <20220926141849.21805-1-jgross@suse.com>
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>
---
arch/x86/xen/enlighten_pv.c | 73 ++++++++++++++++++++++++++++---------
1 file changed, 55 insertions(+), 18 deletions(-)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 0ed2e487a693..4e68e047df94 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -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;
if (pmu_msr_read(msr, &val, err))
return val;
- val = native_read_msr_safe(msr, err);
+ 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;
+
+ if (HYPERVISOR_set_segment_base(which, base) == 0)
+ return;
- ret = 0;
+ 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);
+}
+
+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 ret;
+ return err;
}
static u64 xen_read_msr(unsigned int msr)
--
2.35.3
next prev parent reply other threads:[~2022-09-26 15:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-26 14:18 [PATCH 0/3] xen/pv: sanitize xen pv guest msr accesses Juergen Gross
2022-09-26 14:18 ` [PATCH 1/3] xen/pv: allow pmu msr accesses to cause GP Juergen Gross
2022-09-26 15:29 ` Jan Beulich
2022-09-26 15:33 ` Juergen Gross
2022-09-26 20:09 ` Boris Ostrovsky
2022-09-27 5:42 ` Juergen Gross
2022-09-26 14:18 ` Juergen Gross [this message]
2022-09-26 14:18 ` [PATCH 3/3] xen/pv: support selecting safe/unsafe msr accesses Juergen Gross
2022-09-26 15:23 ` Jan Beulich
2022-09-26 15:36 ` Juergen Gross
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