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path: root/drivers/clocksource/hyperv_timer.c
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Diffstat (limited to 'drivers/clocksource/hyperv_timer.c')
-rw-r--r--drivers/clocksource/hyperv_timer.c61
1 files changed, 47 insertions, 14 deletions
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 18de1f439ffd..c0cef92b12b8 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -367,9 +367,18 @@ static union {
u8 reserved[PAGE_SIZE];
} tsc_pg __aligned(PAGE_SIZE);
+static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page;
+static unsigned long tsc_pfn;
+
+unsigned long hv_get_tsc_pfn(void)
+{
+ return tsc_pfn;
+}
+EXPORT_SYMBOL_GPL(hv_get_tsc_pfn);
+
struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
{
- return &tsc_pg.page;
+ return tsc_page;
}
EXPORT_SYMBOL_GPL(hv_get_tsc_page);
@@ -407,13 +416,12 @@ static void suspend_hv_clock_tsc(struct clocksource *arg)
static void resume_hv_clock_tsc(struct clocksource *arg)
{
- phys_addr_t phys_addr = virt_to_phys(&tsc_pg);
union hv_reference_tsc_msr tsc_msr;
/* Re-enable the TSC page */
tsc_msr.as_uint64 = hv_get_register(HV_REGISTER_REFERENCE_TSC);
tsc_msr.enable = 1;
- tsc_msr.pfn = HVPFN_DOWN(phys_addr);
+ tsc_msr.pfn = tsc_pfn;
hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64);
}
@@ -497,14 +505,10 @@ static __always_inline void hv_setup_sched_clock(void *sched_clock) {}
static bool __init hv_init_tsc_clocksource(void)
{
union hv_reference_tsc_msr tsc_msr;
- phys_addr_t phys_addr;
if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
return false;
- if (hv_root_partition)
- return false;
-
/*
* If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly
* handles frequency and offset changes due to live migration,
@@ -522,18 +526,30 @@ static bool __init hv_init_tsc_clocksource(void)
}
hv_read_reference_counter = read_hv_clock_tsc;
- phys_addr = virt_to_phys(hv_get_tsc_page());
/*
- * The Hyper-V TLFS specifies to preserve the value of reserved
- * bits in registers. So read the existing value, preserve the
- * low order 12 bits, and add in the guest physical address
- * (which already has at least the low 12 bits set to zero since
- * it is page aligned). Also set the "enable" bit, which is bit 0.
+ * TSC page mapping works differently in root compared to guest.
+ * - In guest partition the guest PFN has to be passed to the
+ * hypervisor.
+ * - In root partition it's other way around: it has to map the PFN
+ * provided by the hypervisor.
+ * But it can't be mapped right here as it's too early and MMU isn't
+ * ready yet. So, we only set the enable bit here and will remap the
+ * page later in hv_remap_tsc_clocksource().
+ *
+ * It worth mentioning, that TSC clocksource read function
+ * (read_hv_clock_tsc) has a MSR-based fallback mechanism, used when
+ * TSC page is zeroed (which is the case until the PFN is remapped) and
+ * thus TSC clocksource will work even without the real TSC page
+ * mapped.
*/
tsc_msr.as_uint64 = hv_get_register(HV_REGISTER_REFERENCE_TSC);
+ if (hv_root_partition)
+ tsc_pfn = tsc_msr.pfn;
+ else
+ tsc_pfn = HVPFN_DOWN(virt_to_phys(tsc_page));
tsc_msr.enable = 1;
- tsc_msr.pfn = HVPFN_DOWN(phys_addr);
+ tsc_msr.pfn = tsc_pfn;
hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64);
clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
@@ -566,3 +582,20 @@ void __init hv_init_clocksource(void)
hv_sched_clock_offset = hv_read_reference_counter();
hv_setup_sched_clock(read_hv_sched_clock_msr);
}
+
+void __init hv_remap_tsc_clocksource(void)
+{
+ if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
+ return;
+
+ if (!hv_root_partition) {
+ WARN(1, "%s: attempt to remap TSC page in guest partition\n",
+ __func__);
+ return;
+ }
+
+ tsc_page = memremap(tsc_pfn << HV_HYP_PAGE_SHIFT, sizeof(tsc_pg),
+ MEMREMAP_WB);
+ if (!tsc_page)
+ pr_err("Failed to remap Hyper-V TSC page.\n");
+}