MIPS: KVM: Override guest kernel timer frequency directly

The KVM_HOST_FREQ Kconfig symbol was used by KVM guest kernels to
override the timer frequency calculation to a value based on the host
frequency. Now that the KVM timer emulation is implemented independent
of the host timer frequency and defaults to 100MHz, adjust the working
of CONFIG_KVM_HOST_FREQ to match.

The Kconfig symbol now specifies the guest timer frequency directly, and
has been renamed accordingly to KVM_GUEST_TIMER_FREQ. It now defaults to
100MHz too and the help text is updated to make it clear that a zero
value will allow the normal timer frequency calculation to take place
(based on the emulated RTC).

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: Sanjay Lal <sanjayl@kymasys.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/Kconfig

@@ -1756,14 +1756,14 @@ config KVM_GUEST
 	help
 	  Select this option if building a guest kernel for KVM (Trap & Emulate) mode
 
-config KVM_HOST_FREQ
-	int "KVM Host Processor Frequency (MHz)"
+config KVM_GUEST_TIMER_FREQ
+	int "Count/Compare Timer Frequency (MHz)"
 	depends on KVM_GUEST
-	default 500
+	default 100
 	help
-	  Select this option if building a guest kernel for KVM to skip
-	  RTC emulation when determining guest CPU Frequency.  Instead, the guest
-	  processor frequency is automatically derived from the host frequency.
+	  Set this to non-zero if building a guest kernel for KVM to skip RTC
+	  emulation when determining guest CPU Frequency. Instead, the guest's
+	  timer frequency is specified directly.
 
 choice
 	prompt "Kernel page size"

arch/mips/mti-malta/malta-time.c

@@ -74,18 +74,8 @@ static void __init estimate_frequencies(void)
 	unsigned int giccount = 0, gicstart = 0;
 #endif
 
-#if defined (CONFIG_KVM_GUEST) && defined (CONFIG_KVM_HOST_FREQ)
-	unsigned int prid = read_c0_prid() & (PRID_COMP_MASK | PRID_IMP_MASK);
-
-	/*
-	 * XXXKYMA: hardwire the CPU frequency to Host Freq/4
-	 */
-	count = (CONFIG_KVM_HOST_FREQ * 1000000) >> 3;
-	if ((prid != (PRID_COMP_MIPS | PRID_IMP_20KC)) &&
-	    (prid != (PRID_COMP_MIPS | PRID_IMP_25KF)))
-		count *= 2;
-
-	mips_hpt_frequency = count;
+#if defined(CONFIG_KVM_GUEST) && CONFIG_KVM_GUEST_TIMER_FREQ
+	mips_hpt_frequency = CONFIG_KVM_GUEST_TIMER_FREQ * 1000000;
 	return;
 #endif