[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[PATCH] x86/pv: Make the PV default WRMSR path match the HVM default

  • To: Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • From: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • Date: Thu, 23 Jul 2020 19:26:26 +0100
  • Authentication-results: esa2.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none
  • Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Jan Beulich <JBeulich@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Delivery-date: Thu, 23 Jul 2020 18:26:57 +0000
  • Ironport-sdr: huDvZPas59Cux8i69MV9rDin8lFZkNRXN/fcYdCLfJNG6dTzbtnmBbZXSyObCLxPGbU6sz0uqR DrnU3jqSjlqgTzHUwuuDVm4Ime9uq6gqGSRXCSShg1CySsJe3aDnCNLzzJBKf89svGttKGIWEG Rkxwq+zlgFSeWJ57k5ksdgCjz+W6uazB+b9o5A7ryYNW+pBsD0fw7uJdKtO4nbNGsU8wPCFUqS CNdtugG1M36GOiWc+1QLMR1Wa2qzDLVvB6otzOI9GZCdA5CgzFWD7GTkdTx6Gnpk9ndvrhy5vT zzg=
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

The current HVM default for writes to unknown MSRs is to inject #GP if the MSR
is unreadable, and discard writes otherwise. While this behaviour isn't great,
the PV default is even worse, because it swallows writes even to non-readable
MSRs.  i.e. A PV guest doesn't even get a #GP fault for a write to a totally
bogus index.

Update PV to make it consistent with HVM, which will simplify the task of
making other improvements to the default MSR behaviour.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Jan Beulich <JBeulich@xxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Roger Pau Monné <roger.pau@xxxxxxxxxx>
 xen/arch/x86/pv/emul-priv-op.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/pv/emul-priv-op.c b/xen/arch/x86/pv/emul-priv-op.c
index f14552cb4b..efeb2a727e 100644
--- a/xen/arch/x86/pv/emul-priv-op.c
+++ b/xen/arch/x86/pv/emul-priv-op.c
@@ -1113,7 +1113,10 @@ static int write_msr(unsigned int reg, uint64_t val,
         /* fall through */
-        if ( (rdmsr_safe(reg, temp) != 0) || (val != temp) )
+        if ( rdmsr_safe(reg, temp) )
+            break;
+        if ( val != temp )
                      "Domain attempted WRMSR %08x from 0x%016"PRIx64" to 



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.