[PATCH V2 1/1] X86: hyperv: Enable MSR based APIC access

K. Y. Srinivasan
2015-03-18T20:21:58Z

If the hypervisor supports MSR based access to the APIC registers
(EOI, TPR and ICR), implement the MSR based access.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
Changes from V1: Addressed comments from Ingo Molnar <mingo.kernel.org@gmail.com>

arch/x86/kernel/cpu/mshyperv.c | 62 ++++++++++++++++++++++++++++++++++++++++
1 files changed, 62 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 939155f..76833c6 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -110,6 +110,57 @@ static struct clocksource hyperv_cs = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};

+static u64 ms_hv_apic_icr_read(void)
+{
+ u64 reg_val;
+
+ rdmsrl(HV_X64_MSR_ICR, reg_val);
+ return reg_val;
+}
+
+static void ms_hv_apic_icr_write(u32 low, u32 id)
+{
+ u64 reg_val;
+
+ reg_val = SET_APIC_DEST_FIELD(id);
+ reg_val = reg_val << 32;
+ reg_val |= low;
+
+ wrmsrl(HV_X64_MSR_ICR, reg_val);
+}
+
+static u32 ms_hv_apic_read(u32 reg)
+{
+ u32 reg_val, hi;
+
+ switch (reg) {
+ case APIC_EOI:
+ rdmsr(HV_X64_MSR_EOI, reg_val, hi);
+ return reg_val;
+ case APIC_TASKPRI:
+ rdmsr(HV_X64_MSR_TPR, reg_val, hi);
+ return reg_val;
+
+ default:
+ return native_apic_mem_read(reg);
+ }
+}
+
+static void ms_hv_apic_write(u32 reg, u32 val)
+{
+ switch (reg) {
+ case APIC_EOI:
+ wrmsr(HV_X64_MSR_EOI, val, 0);
+ break;
+ case APIC_TASKPRI:
+ wrmsr(HV_X64_MSR_TPR, val, 0);
+ break;
+ default:
+ native_apic_mem_write(reg, val);
+ }
+}
+
+
static void __init ms_hyperv_init_platform(void)
{
/*
@@ -143,6 +194,17 @@ static void __init ms_hyperv_init_platform(void)
no_timer_check = 1;
#endif

+ if (ms_hyperv.features & HV_X64_MSR_APIC_ACCESS_AVAILABLE) {
+ /*
+ * Setup the hooks for optimized APIC read/write.
+ */
+ apic->read = ms_hv_apic_read;
+ apic->write = ms_hv_apic_write;
+ apic->icr_write = ms_hv_apic_icr_write;
+ apic->icr_read = ms_hv_apic_icr_read;
+ apic->eoi_write = ms_hv_apic_write;
+ }
+
}

const __refconst struct hypervisor_x86 x86_hyper_ms_hyperv = {
--
1.7.4.1