KVM: s390: Enable and disable interrupts in entry code

Move enabling and disabling of interrupts around the SIE instruction to
entry code. Enabling interrupts only after the __TI_sie flag has been set
guarantees that the SIE instruction is not executed if an interrupt happens
between enabling interrupts and the execution of the SIE instruction.
Interrupt handlers and machine check handler forward the PSW to the
sie_exit label in such cases.

This is a prerequisite for VIRT_XFER_TO_GUEST_WORK to prevent that guest
context is entered when e.g. a scheduler IPI, indicating that a reschedule
is required, happens right before the SIE instruction, which could lead to
long delays.

Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Tested-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Andrew Donnellan <ajd@linux.ibm.com>
Reviewed-by: Janosch Frank <frankja@linux.ibm.com>
Signed-off-by: Janosch Frank <frankja@linux.ibm.com>

diff --git a/arch/s390/include/asm/stacktrace.h b/arch/s390/include/asm/stacktrace.h
index 810a6b9d96280f73311de873ad180c59a0cfbd5f..c9ae680a28af910c4703eee179be4db6c1ec9ad1 100644 (file)
--- a/arch/s390/include/asm/stacktrace.h
+++ b/arch/s390/include/asm/stacktrace.h
@@ -66,6 +66,7 @@ struct stack_frame {
                        unsigned long sie_flags;
                        unsigned long sie_control_block_phys;
                        unsigned long sie_guest_asce;
+                       unsigned long sie_irq;
                };
        };
        unsigned long gprs[10];

diff --git a/arch/s390/kernel/asm-offsets.c b/arch/s390/kernel/asm-offsets.c
index a8915663e917faed4551276b64013ee073662cc9..730449f464aff25761264b00d63d92e907f17f78 100644 (file)
--- a/arch/s390/kernel/asm-offsets.c
+++ b/arch/s390/kernel/asm-offsets.c
@@ -64,6 +64,7 @@ int main(void)
        OFFSET(__SF_SIE_FLAGS, stack_frame, sie_flags);
        OFFSET(__SF_SIE_CONTROL_PHYS, stack_frame, sie_control_block_phys);
        OFFSET(__SF_SIE_GUEST_ASCE, stack_frame, sie_guest_asce);
+       OFFSET(__SF_SIE_IRQ, stack_frame, sie_irq);
        DEFINE(STACK_FRAME_OVERHEAD, sizeof(struct stack_frame));
        BLANK();
        OFFSET(__SFUSER_BACKCHAIN, stack_frame_user, back_chain);

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 75b0fbb236d05f420b20cac6bac925e8ac36fa68..e906f4ab6cf35e53061a27192911629c10c347ed 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -189,6 +189,7 @@ SYM_FUNC_START(__sie64a)
        mvc     __SF_SIE_FLAGS(8,%r15),__TI_flags(%r14) # copy thread flags
        lmg     %r0,%r13,0(%r4)                 # load guest gprs 0-13
        mvi     __TI_sie(%r14),1
+       stosm   __SF_SIE_IRQ(%r15),0x03         # enable interrupts
        lctlg   %c1,%c1,__SF_SIE_GUEST_ASCE(%r15) # load primary asce
        lg      %r14,__SF_SIE_CONTROL(%r15)     # get control block pointer
        oi      __SIE_PROG0C+3(%r14),1          # we are going into SIE now
@@ -212,6 +213,7 @@ SYM_FUNC_START(__sie64a)
        lg      %r14,__LC_CURRENT(%r14)
        mvi     __TI_sie(%r14),0
 SYM_INNER_LABEL(sie_exit, SYM_L_GLOBAL)
+       stnsm   __SF_SIE_IRQ(%r15),0xfc         # disable interrupts
        lg      %r14,__SF_SIE_SAVEAREA(%r15)    # load guest register save area
        stmg    %r0,%r13,0(%r14)                # save guest gprs 0-13
        xgr     %r0,%r0                         # clear guest registers to

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 8db37e508a71f31b5e822d7762b9d5422934f90d..4d13601ec2178596c5ba2fcb75ff73b99cf11601 100644 (file)
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -4962,13 +4962,8 @@ int noinstr kvm_s390_enter_exit_sie(struct kvm_s390_sie_block *scb,
         * The guest_state_{enter,exit}_irqoff() functions inform lockdep and
         * tracing that entry to the guest will enable host IRQs, and exit from
         * the guest will disable host IRQs.
-        *
-        * We must not use lockdep/tracing/RCU in this critical section, so we
-        * use the low-level arch_local_irq_*() helpers to enable/disable IRQs.
         */
-       arch_local_irq_enable();
        ret = sie64a(scb, gprs, gasce);
-       arch_local_irq_disable();
 
        guest_state_exit_irqoff();