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

Re: [Xen-devel] [PATCH v3 03/17] xen/arm: vsmc: Implement SMCCC_ARCH_WORKAROUND_1 BP hardening support

On 21/02/18 16:34, Andre Przywara wrote:


On 15/02/18 15:02, Julien Grall wrote:
SMCCC 1.1 offers firmware-based CPU workarounds. In particular,
SMCCC_ARCH_WORKAROUND_1 provides BP hardening for variant 2 of XSA-254

If the hypervisor has some mitigation for this issue, report that we
deal with it using SMCCC_ARCH_WORKAROUND_1, as we apply the hypervisor
workaround on every guest exit.

Signed-off-by: Julien Grall <julien.grall@xxxxxxx>
Reviewed-by: Volodymyr Babchuk <volodymyr.babchuk@xxxxxxxx>

     Changes in v3:
         - Fix minor conflict during rebase

     Changes in v2:
         - Add Volodymyr's reviewed-by
  xen/arch/arm/vsmc.c         | 22 ++++++++++++++++++++--
  xen/include/asm-arm/smccc.h |  6 ++++++
  2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/vsmc.c b/xen/arch/arm/vsmc.c
index 7ec492741b..40a80d5760 100644
--- a/xen/arch/arm/vsmc.c
+++ b/xen/arch/arm/vsmc.c
@@ -18,6 +18,7 @@
  #include <xen/lib.h>
  #include <xen/types.h>
  #include <public/arch-arm/smccc.h>
+#include <asm/cpufeature.h>
  #include <asm/monitor.h>
  #include <asm/regs.h>
  #include <asm/smccc.h>
@@ -93,8 +94,25 @@ static bool handle_arch(struct cpu_user_regs *regs)
          return true;
-        /* Nothing supported yet */
-        set_user_reg(regs, 0, ARM_SMCCC_NOT_SUPPORTED);
+    {
+        uint32_t arch_func_id = get_user_reg(regs, 1);

Shouldn't the function identifier be in x0/r0?

x0/r0 contain the function identifier of the actual function (i.e ARM_SMCCC_ARCH_FEATURES_FID). What we want here is the arch_func_id to check if the firmware implement it. This is the first parameter of the function, according to the calling convention this will be stored in x1/r1.


Julien Grall

Xen-devel mailing list



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